The invention relates to a surfing sail comprising a basic sail whose luff is attached to a mast which is associated in the usual way with a boom to the aft of which is attached the clew of the basic sail and an auxiliary sail which serves reefing purposes. The invention also relates to a boom for a surfing sail of this kind.
The surfing sail according to the invention together with the usual mast and the boom constitutes a surfing sail rig, which is attachable to a surfboard in a manner known per se. To this end the foot of the mast is inserted in an opening which is formed in the surfboard. The opening is usually located in the aft tertiary portion of the surfboard. This kind of assembly is known as a windsurfer or a stand-up sailer.
In order to adjust to the varying wind conditions and wind forces, it is desirable that the sail surface can be varied during sailing in a simple and rapid manner.
There has already been proposed a number of different surfing rigs with reefable sails. These rigs are provided either with detachable sail portions or wound up sails.
As regards the known wound up surfing sails reference is made, for example, to EP-0 139 782 B1.
When a surfing sail is arranged in this manner, that is, for example, it is intended to be wound up around the mast, then it is not possible to use continuous sail battens which are indispensible if a satisfactory sail profile is to be obtained. In addition the wound up sail has frequently a very unsatisfactory profile. Moreover, the rolling up of a sail is time consuming and, normally, it cannot be carried out during surfing.
Furthermore, it is known to make sails from compound sail portions of different sizes, which can be attached to the basic sail. A surfing sail of this kind is described, for example, in DE 39 03 167 A1.
With this kind of surfing sail which consists of assembled sail portions, it is, as a rule, not possible to attach or detach an additional sail portion during sailing. Moreover, the additional sail portion, once detached, has to be carried on the person of the windsurfer. This is inconvenient and impairs the freedom of movement of the surfers.
Furthermore, there is known from DE 38 05 135 a surfing sail rig, which can be reefed during sailing. This known surfing sail rig is provided not only with a sail mast to which is attached a sail but also with a boom mast to which is attached the boom and a tubular cladding having at least one recess for the reefing portion of the sail. The sail is reefed or taken out in that the sail mast is displaced towards the cladding or vice versa.
This construction is not only extremely wasteful and thus expensive, but also unreliable in service and, on top of that, heavy.
A further surfing sail whose size can be varied is described in German Utility Model G 86 08 527.1. This known surfing sail is arranged as a duplex sail, and an auxiliary sail is disposed between the two sail portions and its disposition relative to the duplex sail can be varied. In the reefed condition the auxiliary sail is taken in wholly between the two sail portions and thus it is totally covered up. In the taken out position larger or smaller surfaces of the auxiliary sail project out of the duplex sail so that the total surface of the sail is increased to a greater or lesser extent.
This known surfing sail can be reefed or taken out with great difficulty only, during surfing, because in order to change the position of the auxiliary sail one has to operate several rope ends, for example, the halyard as well as the downhaul, and the sheet.